Metcalfe's Law
A now standard law of network theory that states that the value of any given network is proportional to the square of the number of connected users of that system. In other words, more users increase the value of a network at an exponential rate.
Origin
Robert Metcalfe, co-inventor of Ethernet and co-founder of 3Com, first articulated the principle around 1980 while selling networking equipment. In a 1983 presentation to 3Com's sales force, he used a slide showing that adding nodes cost linearly but added value quadratically. Technology writer George Gilder attributed and popularized the law in a September 1993 Forbes article, giving it the name "Metcalfe's Law."
Everyday Use
A fax machine is useless if only you have one, somewhat useful if ten people have them, and indispensable when millions do. That's Metcalfe's Law: every new user doesn't just get value — they add value for everyone already on the network. It's why social platforms fight so hard for users early on, and why switching away from a dominant network feels impossible once everyone you know is on it.